Dual JSON and XML (de)serialization

This PR contains code updates to templating and web projects to enable DD4T to serialize/deserialize in/from JSON and XML formats. TBBs use the SerializationFormat (default XML) TBB parameter to determine the format to use, the web application checks the appSetting key="DD4T.SerializationFormat" value="JSON/XML", if no app setting is found it uses the first character of the content to determine the deserializer. This allows for a migration of XML TBBs to JSON, and has been tested with XML only, JSON only and hybrid publications for the development of release 2.0 of the SDL Tridion Reference Implementation.

Its based on the serialization only parts of code provided by Quirijn in this branch on subversion: https://dynamic-delivery-4-tridion.googlecode.com/svn/branches/follow-links-per-field